Recently as smart devices have been widely used, users of the smart devices increasingly perform interactions through the smart devices. Smart device users perform interactions, including giving or receiving gifts with others or carrying out financial transactions, by using smart devices.
In particular, building relationships with others or growing personal connections in social networks may be held up as an example of interactions that may be performed by using such smart devices. To build relationships with others and grow personal connections in social networks, users of social network service (SNS) need to send so-called “friend requests” to others. To do so, they have to perform a cumbersome procedure. For example, they have to search a name (or nickname) of other person whom they want to build relationships with, click or touch a button, send a message of friend request to the person and then wait for the person's acceptance. However, it is difficult for users who are not familiar with SNS to perform such procedure. Accordingly, the development of technologies that may solve such problems and perform simple and intuitive interactions is required.